const s = new Set();

[1, 2, 3, 2, 4].forEach(item => s.add(item))
// console.log(s)

let s2 = new Set([1, 2, 3, 5, 4, 4]);
let numbers = [...s2];
// console.log(numbers)

let s3 = new Set([1, 4, 4]);

s3.add(7).add(8)


s3.forEach(console.log)
s3.forEach((a, b, c) => {

})
// set遍历的顺序就是插入的顺序.
